Lacy sustained his second concussion in a year span in last Thursday's 36-16 loss to the Seattle Seahawks. After returning to practice Thursday, Lacy said he may have to eventually change how he runs to last in the NFL, but his between-the-tackles toughness is also what the Packers admire most about the 24-year-old running back.

Gash, who's in his first year as Lacy's position coach, sees no reason why his star pupil should have to change.

Yes, there's a greater emphasis on concussions than ever before. Yes, Lacy feels the effects of every blow he delivers on game day.

So did a guy by the name of Curtis Martin, whom Gash blocked for with the New England Patriots in the mid-90s. He played a decade in the NFL. His 14,101 career rushing yards eventually earning him Hall of Fame status.

"He was a physical runner – 208 pounds – but physical runner that got the tough yards and he played 10 years," Gash said. "You would think that being a smaller back that you would play less than a bigger guy. … The one thing about the NFL, it's the greatest part-time job you'll ever have because nobody's going to do it forever. That's how I always approached the game. Every day was a new day and a different day."

Lacy suffered his first concussion, which he claims was the first of his football career, on his first carry against Washington in Week 2 of last season. That instance was serious business. Lacy blacked out and doesn't remember much after he was leveled by defensive back Brandon Meriweather.

Gash said he never was diagnosed with a concussion during his playing career, but had many of the telltale signs teams look for today.

"I wrote a neck roll. My whole deal is I never thought about tomorrow," Gash said. "I never officially gotten a concussion but have I ever thrown up in the middle of the night and stuff like that? Of course. Have I ever had headaches before a game, after a game, during games? Of course. I'm 45 now and I'm fine.

"It's a big concern now. A kid has a headache, it's stop the press. Let's wait. That's just how it is."

Lacy had only 34 yards on 12 carries before exiting against the Seahawks, but Gash was pleased with how he ran in crediting him for breaking six or seven tackles.

A full participant in Thursday's practice, it'll be up to Lacy this Sunday to help penetrate the New York Jets' large and lengthy line consisting of Muhammad Wilkerson (6-4, 315), Damon Harrison (6-4, 350) and Sheldon Richardson (6-3, 294).

If he's successful, Lacy will do it running with the same tenacity that made him an 1,100-yard rusher last season and the NFL's offensive rookie of the year.

"No, I don't," said Gash when asked if he sees anything that needs to be tweaked. "I'm just here building off of everything that he did last year. The wheel doesn't have to be reinvented because of anything that happened. He works hard. He comes out and gives effort, so I'm not really worried about anything."